As a conventional ventilation system, the vent (2) of FIG. 1 is well known. This vent (2) is aimed to ventilate the attic, under the floor, or a basement of house 1. It is a fixed type vent with a louver cover as illustrated in FIG. 1(A). Under another conventional system, a vent (no illustration) which can be opened and shut manually or by an electric motor is well known. This is mainly used to ventilate a factory or a warehouse.
The conventional fixed-type vent does not have enough opening space due to aesthetics and space constraints of layouts. In addition, since it is continuously open, it cannot ventilate sufficiently and it takes in moisture during the night. This results in mold as well as poor insulation in summer and winter.
Another conventional open/shut vent has better ventilation than that of the fixed type. However, being manually operated, it is difficult to generate the optimum environment in response to climatic changes which occur indoors and outdoors. Moreover, if closing is neglected, it is inevitable that inventory in the warehouse would be seriously damaged.